Table of Contents UNITED STATES SECURITIES AND EXCHANGE COMMISSION FORM 10-Q (Mark One) þ QUARTERLY REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 WASHINGTON, D.C. 20549 For the quarterly period ended September 30, 2019 ☐ TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the transition period from to Commission File Number 001-36569 LANTHEUS HOLDINGS, INC. (Exact name of registrant as specified in its charter) Delaware 35-2318913 (Sta ...